1. Field of the Invention:
The present invention generally relates to a safety device for systems to seal a ship's propeller shaft against the outside water and against a lubrication chamber with a multiple seal. The safety device can be equipped on the outside water side with at least one gasket directed outward, and on the lubrication chamber side with at least one gasket directed inward. Between each two neighboring gaskets a ring-shaped chamber or annulus is reserved, at least one of which chambers is pressurized via a feed line with a gaseous pressure medium, in particular compressed air, whereby the pressure of the pressure medium, by means of a pressure regulation mechanism interposed in the feed line, can be constantly kept slightly lower than the pressure of the outside water and the pressure of the lubricant.
Further, connected to the pressurized ring-shaped chamber there can be a discharge channel which empties into the interior of the ship (bilge), and in which discharge channel there is a controlled shut-off mechanism, preferably a solenoid valve, which shut-off mechanism automatically and periodically opens and closes. The feed of the lubricant to the lubricant chamber takes place from a deep tank, the static level of which can be adjusted by means of a lubricant feed line.
2. Background Information:
In systems of this type, for example, in the system disclosed in German Patent No. 3742079, which patent is hereby incorporated by reference herein, when there is a blockage in the discharge channel, situations can occur in which, for example, a plug is formed from a water-lubricant emulsion which contains particles of dirt and which plug does not leave the discharge channel in spite of the periodic opening and closing of the first shut-off mechanism. Thus, after a certain length of time in operation, due to the underpressure with respect to the outside water pressure and the lubricant pressure, outside water, and possibly also lubricant, penetrates into the ring-shaped chamber, fills it with fluid, which fluid travels through the feed line to the pressure regulation mechanism, thereby adversely affecting the operation of the latter and/or escaping outward through it, which can result in serious damage, malfunctions and disruptions of operations.